The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
The invention firstly relates to an assembly of chain stopper and chain, comprising a housing, a vertically extending chain channel defined in the housing in which a chain is received and guided and two chain lockers positioned at opposite sides of the chain channel, wherein each chain locker is pivotably mounted on a chain locker pivot axis for a rotation between an inwardly rotated position for engaging the chain and preventing a downward shift of the chain in the chain channel, and an outwardly rotated position allowing an upward shift of the chain in the chain channel and wherein each chain locker is biased towards its inwardly rotated position.
In a known assembly of this type (as used, for example, on off shore installations, such as facilities for the production of gas or oil) the bias of the chain lockers towards the inwardly rotated position generally will be caused by gravity (although the use of auxiliary biasing means is not excluded). When the chain has to be lifted, the chain links will rotate the chain lockers outwardly and the chain is free to move upward in the chain channel. A downward movement of the chain is prevented because the chain lockers under influence of gravitational forces again will assume the inwardly rotated position in which they will support a chain link. When in such a known assembly the chain has to be lowered, the chain lockers will have to be locked in the outwardly rotated position. In practise this has been done by the use of divers that used locking devices to be positioned between the chain lockers, or by using less robust mechanisms, such as cables or wires extending to above water line. However, recent legislation and safety regulations may be in conflict with such use of divers which had to operate under dangerous conditions (especially conditions in which the chain already has been lifted for allowing the chain lockers to rotate to the outwardly rotated position).